View Compilation Error

0_0_15829560_16050.cpp: In function 'int main()':
0_0_15829560_16050.cpp:6:9: error: 'cin' was not declared in this scope
   while(cin>>x1>>y1>>x2>>y2)
         ^
0_0_15829560_16050.cpp:8:45: error: 'sqrt' was not declared in this scope
       x=sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
                                             ^
0_0_15829560_16050.cpp:9:7: error: 'cout' was not declared in this scope
       cout<<fixed<<setprecision(2)<<x<<endl;
       ^
0_0_15829560_16050.cpp:9:40: error: 'endl' was not declared in this scope
       cout<<fixed<<setprecision(2)<<x<<endl;
                                        ^